K.B.
Does he have an IEP or any other programs at school? 1 1/2 hours of homework for an "average" student sounds like quite a bit for an 8 year old. I would start with the school. Try to have some of this homework reduced until you can get a handle on the homework routine. One thing that worked for my son at that age (also ADHD) was this. He had a specific seat to do his homework. We went through each item for homework and decided the order it was to be done (simple to hardest worked for us). All items were removed from the vicinity except the one item. We briefly came up with a time limit that it was to be done, I set the timer and stepped away. I never left the room, but I was able to get dinner done, wash dishes, etc. When the timer went off, I checked to see that it was completed and correct and we moved on to the next thing. It took time to get this system working, but it did work. Best of luck and contact me if you have any other questions.